Thanks for the info. Unfortunately, I don't have the ability for
quarantine. My wife won't let me set up another tank in the house.

I seem to have taken care of the agression problem. I doubled the
amount of plants, rearranged the tank, and bought two more juvenile
angels. I added the two new angels to the tank along with the
aggressive one at the same time. After a day or so, everything
settled down.

Now I have two new problems. I treated the tank for a few days with
Melafix and the original new angel's fins have healed nicely.
Unfortunately, he doesn't seem to be eating yet (almost a week now.)

Also, one of my loaches has become sick, coninuous gasping. I changed
about 15% of the water (nitrates aroung 10 ppm after the change) and
added some charcoal/diamond blend to my filter media. Probably too
late. He most likely caught something from one of the new angels.

I knew buying a fully grown angel was a bad idea and shouldn't have
let my wife talk me into it. I've had nothing but grief since.